Wirelessly rechargeable batteries have been used in a range of devices, such as electric toothbrushes, for many years. Such devices typically employ non-standard batteries or are not easily replaceable. Common consumer batteries still typically require galvanic connections to effect recharging. There is a demand for consumer rechargeable batteries that may conveniently be charged wirelessly if placed in a charging region without requiring any special orientation or galvanic connection.
The power receiver needs to be as small as possible to ensure an adequate battery capacity for typical consumer applications. It also needs to be able to couple with a charging alternating magnetic field in any orientation—as the battery may be placed in a charging region in any orientation or may be within a device in any orientation.
The battery also needs to be able to be charged rapidly without overheating of the electrochemical cell in the charging magnetic field.
Further, it would be desirable for the power receiver of the battery to be recyclable or reusable by consumers.
A number or receiver coil topologies have been proposed and are discussed below.
WO 2001/67046 discloses a wireless power receiver with three mutually orthogonal windings wound on a cross shaped core (i.e. the core is the shape of the origin of XYZ coordinate system.
U.S. Pat. No. 5,281,941 discloses a spherical form for supporting three mutually orthogonal windings.
U.S. Pat. No. 7,414,380 discloses a wireless power receiver with three mutually orthogonal wound on a parallipiped shaped core.
U.S. Pat. No. 7,248,017 discloses a wirelessly rechargeable battery with a winding wound on a core outside the battery, or wound on a core and housed inside the battery. The axis of the winding is parallel to the longitudinal axis of the battery. The specification also discloses having two orthogonal windings to give the battery rotational freedom when charging.
US 2011/0086256 discloses a wirelessly rechargeable battery with the receiver circuitry placed in one end of the battery, but the winding is on the outside of the battery.
The above topologies are all somewhat bulky and/or have poor coupling in some orientations. Further, the above designs are integrally formed and do not allow easy reuse. Further, they do not provide shielding of the electrochemical cell.
It is an object of the invention to provide a coil receiver assembly, power receiver and wirelessly rechargeable battery that overcome at least some of these problems or to at least provide the public with a useful choice.